Well, I finally managed to get the lock barrel removed, with a long small screwdriver, a pair of long small pliers, a bright flaslight to see what's where, and the backpain from having to curle under the door, because I am doing this job in front of my house. 
After removing the barrel, the door handle was quick to remove. 
The plastic pieces from the door handle, intended for mounting the screws, have broken. See the photo's. Also the one remaining plastic screw mount, is on the point of breaking, cracks are visible. 
Perhaps this is due to the very extensive anti-rust treatment my TF had, about 5 years ago. Plastic and oil-based coatings,(waxoyl) don't go very well together perhaps. 
Anyway, step 1 is trying to glue it back together with Colad Magic Fix. Our Dutch AA (ANWB) has on my audi fixed a broken cooling pipe with this, better than new. Since then I have done several repairs with this stuff on broken plastic pieces. 
Plan B is to get a new handle, but I need one in X-power grey, could find many colors exepts this one, so that may be difficult. And having one in the wrong color and spray it over is an expensive time consuming. solution. 
Also the simplicity of the door lock mechanism strikes me, reassuring that loosing the key will never prevent me from entering the car, knowing how the internals work. 
Anyway, phase 1 completed, could lock the car with centrail lock and closed the door handle gap with tape, parked the car where this is not immediately visible.